I suggest you try to find a NOS fuel tank sending unit. I'm talking one from the 60's or early 70's, not 2003, or Mexican junk. I had pretty much the same issues for years with my car. Then I decided to fix it right once & for all by finding a NOS sending unit. It took me several months but I did find one. They are still out there. As soon as I pop it in and hook everything back up I had a accurate working gas gauge. Best thing I ever done to my car. Nothing beats a good NOS part.